Exp 7

• Soda ash - is a common name for the inorganic compound, sodium carbonate, with the chemical formula Na2CO3.
• Soda ash, Its anhydrous form has the molar mass of 106 g/mol
• At standard temperature and pressure, soda ash is known to exist as a white solid that is hygroscopic in nature.
• Soda ash is widely used as a cleaning agent for several domestic purposes such as the washing of clothes. It is also known to be an important component of several dry soap powders. It is also a component of baking powder as it releases carbon dioxide gas when heated which makes the baked products rise.
• Soda ash functions as a silica flux , working to reduce the melting point of the mixture without any need for special materials.
• The resulting "soda glass" is slightly water-soluble, so the melt mixture is added with some calcium carbonate to make the glass insoluble.
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  The melting of such blends of sodium carbonate, calcium carbonate, and silica sand(also known as silicon dioxide) creates bottle and window glass (soda-lime glass).
• Soda ash is water-soluble and is known to form slightly alkaline solutions when dissolved in water. This property is what is made used for this method.

• Titrating with standard acid, usually HCI, makes it possible to determine the total alkalinity of the soda ash.
• The indicator to be used for this analysis is methyl orange indicator. At the start of the titration, this indicator appears yellow
• The endpoint is signaled when the indicator turned light orange as shown in the middle flask. Do not allow for the titration to go to a very deep orange like the one shown in the left flask.
• second end point - is always used for analysis because the change in pH is greater than that at the first.
• An even sharper end point can be achieved by boiling the solution briefly to eliminate carbonic acid and carbon dioxide, the reaction products.
• The sample is titrated to the first appearance of the acid color of the indicator.
• At this point, the solution contains a large amount of dissolved carbon dioxide and small amounts of carbonic acid and unreacted hydrogen carbonate. Boiling effectively destroys this buffer by eliminating the carbonic acid.
• The solution then becomes alkaline again due to the residual hydrogen carbonate ion . The titration is completed after the solution has cooled, resulting in a substantially larger decrease in pH during the final additions of acid. A more abrupt color change is the result.